> Only catch is that it hasnt been directly observed.
Ok, so... why do people take it seriously as a concept? Occam's razor would point towards some general misunderstanding on which we have no evidence to reasonably speculate a cause.
> Only catch is that it hasnt been directly observed.
Ok, so... why do people take it seriously as a concept? Occam's razor would point towards some general misunderstanding on which we have no evidence to reasonably speculate a cause.
> Occam's razor would point towards some general misunderstanding on which we have no evidence to reasonably speculate a cause.
For some general misunderstanding to explain what we see, ie something which is not dark matter, it means our equations of gravity must be wrong.
People have tried hard to tweak the equations to fix the observations. One such proposal is indeed MOND that the submission is about.
The problem with tweaking the equations is that we have a lot of observations of very different circumstances and scales, and it's so far proved impossible to tweak the equations in a given way so they explain all of the observations. What happens is that you can tweak them so they fit one set of observations, like MOND fitting galaxy rotation curves, but then not fit other sets of observations, like MOND with the motion of galaxies in galaxy clusters as discussed in the submission.
Meanwhile, adding dark matter seems to work much better at explaining all the observations at once. I say much better because there is still some tension, but it's way less than any modifications of gravity.
Having dark matter particle(s) is also not that strange. As far as we know there's no requirement that a particle interacts with any of the known forces beyond gravity. And while the early particle candidates seem to be getting ruled out, axion-like particles, originally proposed to solve entirely different problems, are still a good dark matter candidate.
That said, it's not settled. People are proposing alternatives. One example I know of is Alexandre Deur[1], a QCD physicist which has taken his QCD knowledge into the realm of GR and proposed that perhaps graviton-graviton self-interaction can explain a lot of the dark matter phenomena. It's not mainstream, but he's getting published in peer-reviewed journals.
[1]: https://arxiv.org/search/gr-qc?searchtype=author&query=Deur,...
> Having dark matter particle(s) is also not that strange. As far as we know there's no requirement that a particle interacts with any of the known forces beyond gravity.
This is the key thing. As we still don't have a theory of everything, which explains the fundamental reasons why every particle is the way it is, dark matter is a very straightforward and simple explanation.
The name makes it sound stranger than it is. It's just particles that have mass and are affected normally by gravity, but which are unaffected by the electromagnetic force.
It's not a particularly exotic or implausible or wild idea. In fact it's so simple it's almost boring. It's just obviously inherently difficult to test directly, since gravity is such a weak force.
> Occam's razor would point towards some general misunderstanding on which we have no evidence to reasonably speculate a cause.
Dark matter is the Occam's Razor theory. It explains almost all of the observations while assuming the least.
Why do you assume we have no evidence just because we don't have direct observations? Black holes were a similar phenomenon that we had no direct evidence for a fairly long time even though we had lots of other indirect phenomenon that really couldn't be explained any other way.
The razor is commonly misunderstood.
William of Ockham objected to his fellow theologians inventing things out of whole cloth (like dark matter question mark). That’s the point, not that a simpler explanation is more likely to be true.
The common understanding would have us believe that creationism, being simpler, outshines evolution, or that there is no such thing as a color revolution because the simplest explanation is that the mass protests are earnestly aggrieved locals.
Yours is a common misunderstanding, as well.
Occam's Razor only kicks in when the hypotheses have equal predictive and explanatory power.
The MOND hypothesis does NOT have equal explanatory power with the dark matter hypothesis. As such, Occam's Razor is not relevant.
Maybe you can point me to the "equal predictive and explanatory power" bit in William's writings.
Because the discrepancy exists and shows consistency. This gap needs to be called something, you can't just pretend it's not real. But the underlying model seems fine and all alternatives are broken.
So we came up with an idea that fills the gap in the current model and allows us to continue predictive science until we find out more.
People get so absurdly touchy about Dark Matter just because it's named and "weird". It's just a placeholder value.
Because stuff like the Bullet Cluster exists. Dark matter is in fact the simplest answer.
https://en.wikipedia.org/wiki/Bullet_Cluster
I feel compelled to point out that (a)ether was the simplest answer until we confirmed that space is a vacuum and that light can travel in the absence of a medium.
Abandoning aether was NOT a "simple" answer. One you abandon aether, all manner of weirdness suddenly pops in.
Light being the same speed irrespective of observer is weird. Velocity dilating length and time is weird. Not having a preferential observation point is weird. Not needing a medium for transmission is weird. Not being able to agree on simultaneity is weird. etc.
Aether wasn't just something that a bunch of dullards clung to. You have to abandon some very long held common-sense understanding when you give it up.
That's my point exactly.
aether was not the simplest explanation since it was disproved by Michelson-Morley experiment. Nothing as of now yet has disproved Dark matter as thoroughly.
The two were dealt with very differently.
Aether: observations show lack of aether so we update the theory that makes aether unnecessary.
Dark matter: observations show lack of observable matter so we keep hunting for decades locating it. The aether analogue would have been to continue to look for dark aether. Dark matter is more like god of gaps. We can 'darkify' any theory that does not fit empirical evidence.
It's hard to tell now which leans more towards the more correct theory.
Angry gods used to be the simplest answer for a lot of things. Inevitably we find a better model
You are of course very welcome to propose this supposed better model, but please do some due diligence and learn to roughly understand the current flawed models firsts.
For example "angry gods" was never a simple theory, one needs only to read some fan fiction to understand that theology gets complicated fast. Instead "angry gods" is a simplified summary of a very complicated theory about metaphysical hierarchy, creation, agency, the meaning of divinity, and cause and effect, etc etc.
Simplest in this sense does also imply predictability for Dark matter, which cannot be said for angry gods. Angry gods is anything but a simple theory.
We already know that some particles interact extremely weakly with others. Neutrinos were postulated as a "dark" particle in order to preserve conservation of energy and momentum, but it took more than a decade before they were observed directly. There's no reason there couldn't be another particle with an even weaker interaction.
It doesn't even matter whether it actually exists, because it works for modeling the universe and making accurate predictions about it.
That means for now it's useful.
We have indirectly observed it a bunch, and our understanding of physics allow the existence of material that flatly cannot be directly observed.
A "general misunderstanding" isn't really a theory whose complexity you can compare to the Dark Matter theory.
One could also argue that on the one hand you need just one concept (dark matter) to explain three phenomena (galaxy rotation curves, gravitational lensing, CMBR), and the "general misunderstanding" might need to have three aspects to make it explain all three things, making it more complex.
Occam's razor is a good guiding principle, but in some cases, it's really hard to compare the complexity of competing theories. My favorite example of this is the Many Worlds interpretation of quantum mechanics. In some sense, it's really simple, the wave function just follows the Schrödinger equation. In another sense, it implicitly postulates the existence of many parallel worlds, which you can count as a quasi-infinite complexity penalty, or you can shrug and say it's not a big deal, the theory says the parallel worlds aren't observable, so there is nothing wrong with postulating them. There's no objective way to decide that.
>Occam's razor would point toward...
Occam's razer is not a thing with explanatory or legal or even scientific force. if Occam's razor was really a thing, quantum theory and general relativity would be ruled out as complicated and neither 100 percent explanatory.
> Ok, so... why do people take it seriously as a concept?
Historically, science has predicted lots of true things about the universe that could not be observed at the time.
> Historically, science has predicted lots of true things about the universe that could not be observed at the time.
Just some examples I could think of:
The neutrino[1], predicted in 1930 due to missing mass in beta decays, discovered in 1956.
Gravitational waves[2], predicted by Einstein in 1916, indirectly detected via pulsars in 1974 and directly by LIGO in 2015.
Higgs boson[3], predicted in 1964 to solve the problem of the Standard Model at the time requiring particles to be massless, which we knew they weren't. Hints from LEP at the turn of the millennium, detection by the LHC in 2012.
Cosmic microwave background[4], predicted in 1948 as a consequence of the expanding universe on the early radiation. Detected by accident in 1964.
Gravitational lensing[5] was first proposed in 1801 as a consequence of Newtonian corpuscular theory of light. Einstein realized in 1915 that GR predicted a larger value. Weak lensing by the sun was observed in 1919. Strong lensing by a distant galaxy of an object behind the galaxy was was predicted in 1937, and first observed in 1979.
[1]: https://en.wikipedia.org/wiki/Neutrino#Pauli's_proposal
[2]: https://en.wikipedia.org/wiki/Gravitational_wave#History
[3]: https://en.wikipedia.org/wiki/Higgs_boson#History
[4]: https://en.wikipedia.org/wiki/Cosmic_microwave_background#Hi...
[5]: https://en.wikipedia.org/wiki/Gravitational_lens#History
I don't know what or why our science education is like this, but it seems like everybody's understanding of science bottomed out at a straw man version of popper & positivism.
And to be clear, falsification and being empirical & skeptical about theoretical claims is great. What I see all too often on the Internet is just pattern matching to the words "observable" and "falsification" without a second thought, without actually looking into how science develops, and any and all narratives are historically rewritten to fit only those two categories.
Which is why it's even more impressive to be a real scientist, to actually be able to navigate the muddy waters properly where it's not just some simple adjective checklists to run through. (As a non scientist)
I feel the same, but then I remind myself of how I used to feel about dark matter (I really disliked it). Having an arena where no scientific question is out of bounds is great.
I blame sci-fi.
As a kid in 90s who was into this stuff, it seemed like anyone who knew about dark matter knew it was just theorized and never observed. It was included as a caveat in a lot of things I read to ensure the readers understood this.
Then in sci-fi it started showing up as a material the characters would interact with, and a lot more people were introduced to the term.
Then as a teen in the 2000s the caveat was usually gone and it started being treated as something we had proof of. People I knew started thinking it was something we'd actually found and was now fact instead of theory.
> Ok, so... why do people take it seriously as a concept? Occam's razor would point towards some general misunderstanding on which we have no evidence to reasonably speculate a cause.
One scientist says "We don't know, really, it's a head scratcher" and the others say something cool like "Dark energy", which ones will get more attention and publicity?
But it really isn't a head scratcher, and it's not a wild guess, and also, dark matter is not the same as dark energy.
Think about some random person born in the 1950s. It will be impossible for you to directly prove that that person has two parents, but with all your knowledge about biology, and your knowledge that humans could not be cloned in the 1950s, it's not a head scratcher, unless our understanding of biology is completely off, it's not just speculation there were two parents. That's the comparable situation with dark matter. It's not a head scratcher. Every indication shows there is a lot of mass around that doesn't interact with light.